1. Field of the Invention
This invention relates to a flexible structural restraint layer for use with an inflatable module structure. The inflatable module structure has a rigid structural core and utilizes a flexible inflatable bladder. The flexible structural restraint layer works in conjunction with the bladder. In practice, the flexibility of the restraint layer is derived from utilizing flexible straps. The restraint layer surrounds the bladder and the restraint layer functions as a structure that distributes substantially the load from the bladder when the bladder is fully inflated. Loads are distributed from the restraint layer to the rigid structural core. In this way, the bladder experiences less stress when fully inflated.
2. Description of the Prior Art
Inflatable modular structures are well known in the art. For example, U.S. Pat. No. 6,439,058 to Taylor illustrates a module with a flexible shell and a bladder for inflation when deployed in space. While various aspects of the shell are identified, i.e. debris shield and bladder, no claim is drawn to a flexible restraint layer. Further, while the patent makes reference to a flexible restraint comprised of a weave of straps as part of the TransHab concept derived by NASA, none of the claims are drawn to this invention and no specific details are illustrative of this concept.
U.S. Pat. No. 6,231,010 to Schneider, et al, also addresses an inflatable modular structure. The Schneider invention does make reference to a structural restraint layer and claims a structural restraint as part of the module invention. However, there are no claims exclusively to the restraint layer and no mention is made as to the use of straps as part of the structural restraint layer.
U.S. Pat. No. 6,547,189 to Raboin, et al, identifies a structural restraint layer comprised of straps as part of an inflatable module. The restraint layer identified is drawn only to a weave of straps. Further, there are no claims drawn specifically to just the restraint layer. The woven strap restraint layer is identified as part of the module as a whole.
The drawback of the Raboin invention lies within the use of a weave of straps. Typically, the most efficient distribution of a load using a strap is where the load is applied along the length of the strap. As a strap is twisted or coiled, a portion of the load is directed away from the length of the strap. In this situation a load would be applied in an area that may not be specifically engineered to handle the load. This creates stress points along the strap where the strap is bent and that can lead to a failure of the strap. In a weave of straps, each strap is bent in numerous locations to conform to other straps in the weave. These bends can increase the possibility of failures.
A further drawback with the use of a weave is the amount of weight resulting from the number of straps being employed. In the weave are a large number of longitudinal strap (also referred to as an axial strap) to weave with the hoop straps. This is effectively a double layer of straps. As launch costs presently can be of the order of $10,000.00 per pound, this increased weight has an adverse fiscal impact.
Thus, the present invention has the distinct advantages of reducing the potential stress points on a strap and results in an assembly that has less weight and thereby reduces the cost to place a module in orbit.